(a) Field of the Invention
The present invention relates to an inspection apparatus of an electrolyte membrane, and more particularly, to an inspection apparatus of an electrolyte membrane that quantitatively measures a position and size of a pinhole formed at an electrolyte membrane of a fuel cell stack.
(b) Description of the Related Art
As is generally known, a fuel cell system is a type of power generation system that directly converts chemical energy of a fuel to electrical energy. In a fuel cell stack that is applied to a fuel cell vehicle, unit cells are continuously arranged (e.g., stacked), and a Membrane-Electrode Assembly (MEA) is disposed at the innermost of each unit cell. The MEA is formed with an electrolyte membrane that moves protons, and a catalyst layer, i.e., a cathode and an anode, which is coated for reaction of hydrogen and oxygen at respective surfaces of the electrolyte membrane.
Generally, the electrolyte membrane is formed of a perfluorosulfonic acid-based material, and a very thin membrane (e.g., about 10-30 micrometers) is used to decrease ion conductivity influencing performance of the fuel cell. A gas diffusion layer (GDL) is disposed at both sides of the membrane electrode assembly. A separating plate at which a flow field is formed is disposed extraneous to the gas diffusion layer to supply fuel and air to the cathode and the anode and discharge water generated by the chemical reaction. Sub-gaskets are disposed at both sides of the catalyst layer and are used to handle the membrane-electrode assembly.
When the fuel cell stack is operated long-term under an abnormal situation (e.g., when the temperature of the fuel cell stack is increased by non-uniform cooling of the fuel cell stack, or when the temperature of the fuel cell stack is increased by inverse voltage), thickness of the electrolyte decreases and thus air-tightness between hydrogen and air is deteriorated. Therefore, pinholes (e.g., apertures or bores) are formed at the electrolyte membrane. In particular, air directly contacts hydrogen due to the pinholes and a high temperature combustion reaction occurs. Therefore, the size of the pinhole increases, and thus the fuel cell stack is damaged.
Additionally, the pinholes may be generated in a manufacturing process of the electrolyte membrane, a bonding process of the catalyst layer and the gas diffusion layer, or a bonding process of the sub-gaskets. When the size of the pinholes is substantial, a worker may verify a position and size of the pinholes with the naked eye. However, when the size of the pinholes is very small (e.g., less than a predetermined size), the thickness of the electrolyte membrane decreases, or the electrolyte membrane is partially damaged, and thus, the worker cannot verify the position and size of the pinholes, a portion where the electrolyte membrane is decreasing, or a portion where the electrolyte membrane is partially damaged. Therefore, an inspection apparatus configured to quantitatively measure the pinholes, the portion where the electrolyte membrane is decreasing, or the portion where the electrolyte membrane is partially damaged is required.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.